Shoe having shoe sole with divided rear foot portion

ABSTRACT

A sole includes a rear end portion on a rear end side, and a rear portion arranged anterior to the rear end portion; a rear surface of the rear portion includes one inclined surface extending in an upper-rear diagonal direction; a front surface of the rear end portion includes another inclined surface extending in an upper-rear diagonal direction; the inclined surface of the rear portion and the inclined surface of the rear end portion together define a first divide portion at which the surfaces are in contact with each other or are capable of contacting each other; and the inclined surface of the rear end portion is set so that the inclined surface is rotatable relative to the inclined surface of the rear portion in such a manner that a lower portion of the divide portion opens.

TECHNICAL FIELD

The present invention relates to a shoe having a shoe sole with a divided rear foot portion.

BACKGROUND ART

Shoes allowing users to run with a barefoot feel have recently been gaining popularity among some fans. These shoes are made to pursue a barefoot feel.

Barefoot-feel shoe soles are thin, and such thin shoe soles will lower the shock-absorbing property.

CITATION LIST Patent Literature

First Patent Document: JP3,119,977U (front page)

Second Patent Document: JP2007-89734A (front page)

Third Patent Document: JP2000-197503A (front page)

Fourth Patent Document: JP11-123101A (front page)

Fifth Patent Document: JP2001-70004A (front page)

Sixth Patent Document: JP2010-504839W (front page)

Seventh Patent Document: WO2013/168259A1 (front page)

WO2013/168259A1 proposes a shoe allowing the user to run without stress while maintaining its shock-absorbing property. This shoe is expected to suppress pronation of the heel portion (eversion) occurring during the landing period while running, while maintaining its shock-absorbing property.

SUMMARY OF INVENTION

However, this prior technique is not a proposal that pursues a barefoot feel. Therefore, it is not possible to realize barefoot-running joint movements.

Therefore, it is an object of the present invention to provide a shoe that realizes foot joint movements close to barefoot-running joint movements while realizing a better shock-absorbing property than when running barefoot.

The present invention is directed to a shoe including an upper 8 wrapping around an instep of a foot, and a main sole MS supporting a sole of the foot, wherein:

the main sole MS includes a rear end portion 13 on a rear end side, and a rear portion 12 arranged anterior DF to the rear end portion 13;

a rear surface of the rear portion 12 includes one inclined surface 12B extending in an upper-rear diagonal direction;

a front surface of the rear end portion 13 includes another inclined surface 13B extending in an upper-rear diagonal direction;

the inclined surface 12B of the rear portion 12 and the inclined surface 13B of the rear end portion 13 together define a divide portion D2 at which the inclined surface 12B of the rear portion 12 and the inclined surface 13B of the rear end portion 13 are in contact with each other or are capable of contacting each other; and

the inclined surface 13B of the rear end portion 13 is set so that the inclined surface 13B is rotatable relative to the inclined surface 12B of the rear portion 12 in such a manner that a lower portion of the divide portion D2 opens (widens).

As used in the present specification, inclined surfaces being in contact with each other means that at least a portion of one inclined surface is in contact with at least a portion of the other inclined surface when not worn. In this case, the load of the forefoot section when worn can easily be supported by the main sole MS.

On the other hand, inclined surfaces being capable of contacting each other means that during the transition from heel-contact to heel-rise when worn, preferably at least at the stationary standing position ((load/shoe size)=1 kgf/cm), at least a portion of one inclined surface is in contact with at least a portion of the other inclined surface. In this case, the minimum value of the distance between these surfaces when not worn is preferably greater than 0.0 mm and less than 2.0 mm, and more preferably less than 1.0 mm, and most preferably less than 0.5 mm.

In the present invention, during the period of transitioning from heel-contact, where only the heel contacts the ground, to foot-flat, where the sole of the foot entirely contacts the ground, the rear portion 12 and the rear end portion 13 can rotate relative to each other with the divide portion D2 therebetween. This rotation will likely allow rotation of the subtalar joint STJ and the midtarsal joint MTJ of the foot.

Thus, the divided main sole MS allows flexion and rotation of various joints. As a result, one is likely to enjoy a running feel that is close to a barefoot feel.

Note that the third and fourth inclined surfaces 12B, 13B of the divide portion D2 extend in an upper-rear diagonal direction, and the third portion 13, which receives the load immediately after landing, therefore has a shape that flares downward. Therefore, the load will be easily supported by the third portion 13.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a medial side view showing a shoe according to one embodiment of the present invention.

FIG. 2 is a lateral side view showing the same. Note that in FIG. 1 and FIG. 2, areas where mesh fabric is exposed is dotted.

FIG. 3 is a perspective view showing a shoe sole as seen from the bottom surface side.

FIG. 4 shows a bottom surface of the shoe sole.

FIG. 5 is a plan view showing a midsole.

FIG. 6A, FIG. 6B, FIG. 6C, FIG. 6D, FIG. 6E, FIG. 6F and FIG. 6G are cross-sectional views taken along respective lines shown in FIG. 4.

FIG. 7 is an exploded perspective view of a midsole showing a first portion to a third portion separated from each other.

FIG. 8 is an exploded perspective view showing an insole separated from a main sole. Note that in FIG. 8, the surface of the paddle is dotted.

FIG. 9 is a lateral side view showing the shoe at heel-rise.

FIG. 10 is a lateral side view showing the shoe at heel-contact.

FIG. 11A, FIG. 11B and FIG. 11C are a medial side view, a plan view and a lateral side view, respectively, showing the foot bone structure.

FIG. 12A and FIG. 12B are a back view and a perspective view of a worn shoe showing pronation and internal (medial) rotation of the foot, respectively.

FIG. 13A, FIG. 13B, FIG. 13C, FIG. 13D and FIG. 13E are schematic lateral side views showing respective test samples. Note that in these figures, flexible portions are dotted.

FIG. 14A, FIG. 14B and FIG. 14C are graphs showing test results.

FIG. 15A, FIG. 15B and FIG. 15C are graphs showing test results.

FIG. 16 is a lateral side view showing a shoe according to an alternative embodiment.

FIG. 17A, FIG. 17B, FIG. 17C, FIG. 17D, FIG. 17E, FIG. 17F and FIG. 17G are cross-sectional views showing other alternative embodiments.

DESCRIPTION OF EMBODIMENTS

Preferably, the divide portion D2 includes a diagonal portion 181 extending, from a central portion 13C in a medial-lateral direction, in an anterior DF-lateral diagonal direction.

In this case, the diagonal portion 131 of the divide portion D2 is likely to extend along a plane that intersects the axis of the subtalar joint STJ or the midtarsal joint MTJ. Therefore, at the divide portion D2, the inclined surfaces 12B, 13B rotate about the axis relative to each other, which will more likely allow rotation of the joints.

More preferably, an angle α formed between a virtual transverse line VL perpendicular to a central axis S, which extends in a front-rear direction FB of the main sole MS, and the diagonal portion 131 of the divide portion D2 is set in a range of 10° to 40°.

The diagonal portion 131, which is set in such an angle range, is likely to extend along planes that intersect the axes of the joints, which will more likely allow relative rotation about the axes of the joints.

Preferably, a medial edge 1M of the divide portion D2 is arranged rearward of a lateral edge 1L of the divide portion D2.

With such an arrangement, the inclined surfaces 12B, 13B, which form the divide portion D2, will likely extend along the intersecting planes. This will more likely allow relative rotation about the axes of the joints.

Preferably, the shoe further includes:

an insole 4 being continuous with the upper 3 and covering the sole of the foot, the main sole MS covering the insole 4 from below; and

a bridging portion 5B provided so as to bridge between the rear portion 12 and the rear end portion 13 across the divide portion D2, wherein the bridging portion 5B connects between the rear portion 12 and the rear end portion 18 so that the inclined surface 12B of the rear portion 12 is rotatable relative to the inclined surface 13B of the rear end portion 13, wherein:

a part of the bridging portion 5B is arranged between the insole 4 and the rear portion 12; and

another part of the bridging portion 5B is arranged between the insole 4 and the rear end portion 13.

In this case, the bridging portion 5B that connects together the rear portion 12 and the rear end portion 13 is arranged between the insole 4 and the rear portion 12 and arranged between the insole 4 and the rear end portion 13. Therefore, the rear portion 12 and the rear end portion 18, which are connected together via the bridging portion 5B, can easily be positioned with respect to each other. This as a result improves the positioning precision between the main sole MS and the upper 3, and the performance will be unlikely to vary from one product to another.

Preferably, the bridging portion 5B is formed from a plate-shaped member that is different (separate) from the main sole MS.

In this case, it will be easier to manufacture the shoe sole, as compared with a case in which the bridging portion 5B is formed from the main sole MS.

More preferably, the shoe further includes one engagement portion 12E and another engagement portion 13E for positioning the bridging portion 5B, wherein the one engagement portion 12E is formed on an upper surface of the rear portion 12, and the other engagement portion 13E is formed on an upper surface of the rear end portion 13.

In this case, the bridging portion 5B is easily positioned with respect to the rear portion 12 and the rear end portion 13. This as a result will further improve the positioning precision between the rear portion 12 and the rear end portion 13.

More preferably, the rear portion 12 and the rear end portion 13 define respective depressions into which the bridging portion 5B fits, the depression of the rear portion and the depression of the rear end portion form the one engagement portion 12E and the other engagement portion 1E, respectively.

In this case, the bridging portion 5B fits in the depressions of the rear portion 12 and the rear end portion 13, and can therefore be easily positioned. This as a result will further improve the positioning precision between the rear portion 12 and the rear end portion 18.

Preferably, an elastic modulus of the bridging portion 5B is equal to or greater than an elastic modulus of the insole 4.

In this case, the bridging portion 5F having a large elastic modulus (Young's modulus) will suppress the inadvertent upward relative warping of the rear end portion 13 with respect to the rear portion 12.

Preferably, the bridging portion 5B defines a through hole 5H, the through hole 5H being arranged so as to extend from the rear portion 12 to the rear end portion 13.

In such a case, the main sole MS can easily flex at the bridging portion 5B.

Preferably, a width Wb of the bridging portion 5B in the divide portion D2 is set to be 25% to 100% of a width W of the main sole MS.

The bridging portion 5B having a large width Wb improves the positioning precision.

Preferably, a thickness of the bridging portion 5B is set to be 0.1 mm to 5.0 mm.

In this case, the bridging portion 5B being thin contributes to maintaining a light weight, and awkwardness is unlikely to be felt on the sole of the foot.

Preferably, the rear portion 12 extends toward a front direction DF from the rear surface, the rear portion 12 defines a groove 12G anterior DF to the rear surface, and the groove 12G is shallower than a depth of the divide portion D2 and extends in a width direction W of the main sole MS.

In this case, the main sole MS can easily twist in the rear portion 12, which will more likely allow relative rotation about the axes of the joints.

Preferably, a medial surface 31 of the upper 3 includes a medial high-rigidity portion 31H and a medial flexible portion 31S that bends more easily than the medial high-rigidity portion 31H, wherein the medial high-rigidity portion 31H and the medial flexible portion 318S are separated from each other in a front-rear direction;

a lateral surface 32 of the upper 8 includes a lateral high-rigidity portion 32H and a lateral flexible portion 32S that bends more easily than the lateral high-rigidity portion 32H, wherein the lateral high-rigidity portion 32H and the lateral flexible portion 32S are separated from each other in a front-rear direction;

a front edge portion of the medial high-rigidity portion 31H and/or the medial flexible portion 31S extend in an upper-rear diagonal direction from an upper end portion of a medial edge 1M of the divide portion D2; and

a front edge portion of the lateral high-rigidity portion 32H and/or the lateral flexible portion 32S extend in an upper-rear diagonal direction from an upper end portion of a lateral edge 1L of the divide portion D2.

At heel-contact immediately after landing, an area of the upper 3 that is in an upper-rear diagonal direction of the divide portion D2 is compressed as the rear end portion 13 rotates relative to the rear portion 12 of the main sole MS. Since the upper 3 of this example includes the flexible portions 328, 31S, the flexible portions 328, 318 will easily contract (creating creases) at heel-contact. Thus, the rotation at the divide portion D2 is unlikely to be inhibited.

Preferably, a strip-shaped restraining member 34M is arranged on the medial-side flexible portion 31S for restraining stretch of the medial-side flexible portion 31S in a front-rear direction FB; and

another strip-shaped restraining member 84L is arranged on the lateral-side flexible portion 32S for restraining stretch of the medial-side flexible portion 31S in a front-rear direction FD.

At heel-rise, the heel of the foot is likely to rise inside the upper 3. While the flexible portions 328, 31S (FIG. 1) are present, the restraining members 34L, 34M are provided on the flexible portions 328, 31S. Therefore, it is possible to restrain the stretch of the flexible portion of the upper 3 at heel-rise, and it is therefore possible to prevent the heel from rising inside the upper 3.

Any feature illustrated and/or depicted in conjunction with one of the aforementioned aspects or the following embodiments may be used in the same or similar form in one or more of the other aspects or other embodiments, and/or may be used in combination with, or in place of, any feature of the other aspects or embodiments.

EMBODIMENTS

The present invention will be understood more clearly from the following description of preferred embodiments taken in conjunction with the accompanying drawings. Note however that the embodiments and the drawings are merely illustrative and should not be taken to define the scope of the present invention. The scope of the present invention shall be defined only by the appended claims. In the accompanying drawings, like reference numerals denote like components throughout the plurality of figures.

Embodiment 1 of the present invention will now be described with reference to FIG. 1 to FIG. 10.

The present embodiment is directed to a shoe sole of a shoe for running or walking, for example.

A main sole MS shown in FIG. 1 includes a rubber-made outsole 2 and a resin-made midsole 1. An upper 3 wrapping around the instep of the foot is provided over the main sole MS.

The midsole 1 includes a midsole body made of a resin-made foamed material such as EVA, for example, and may further include a reinforcement device. The term “made of resin” means that a resin component such as a thermoplastic component is contained, and may include any other suitable component. A paddle 5 of FIG. 8 made of a high-resilience material, for example, is provided on the upper surface of the midsole 1.

The outsole 2 of FIG. 1 is a tread sole having a higher abrasion resistance than the foamed material of the midsole body, and typically has a higher hardness than the foamed material of the midsole body. Note that the term “made of rubber” means that it contains a natural rubber component or a synthetic rubber component, and it may contain any other component.

As shown in FIG. 3 to FIG. 5, the midsole 1 of the present embodiment and the insole 4 of FIG. 8 generally cover the entire surface of the sole of the foot. On the other hand, as shown in FIG. 1 and FIG. 2, the outsole 2 is attached to the lower surface of the midsole 1 and partially covers the sole of the foot. That is, the main sole MS of FIG. 8 including the midsole 1 and the outsole 2 covers the insole 4 from below and supports the sole of the foot.

The insole 4 of FIG. 8 and FIG. 6B to FIG. 6G is continuous with the upper 3 of FIG. 2. The upper 3 is shaped so as to wrap around the instep of the foot. Note that the shoe may include a shoelace for fitting the upper 3 to the foot.

The main sole MS is divided into a toe-side first portion 11, a second portion (rear portion) 12 arranged posterior DB to the first portion, and a third portion 13 (rear end portion) on the rear end side.

The rear surface of the first portion 11 includes a first inclined surface 11F extending in an upper-front diagonal direction. The front surface of the second portion 12 includes a second inclined surface 12F extending in an upper-front diagonal direction. The first inclined surface 11F and the second inclined surface 12F together define a first divide portion D1 at which the surfaces 11F, 12F are in contact with each other or are capable of contacting each other.

The rear surface of the second portion 12 includes a third inclined surface 12B extending in an upper-rear diagonal direction. The front surface of the third portion 13 includes a fourth inclined surface 13B extending in an upper-rear diagonal direction. The third inclined surface 12B and the fourth inclined surface 13B together define a second divide portion D2 at which the surfaces 12B, 13B are in contact with each other or are capable of contacting each other.

The midsole 1 and the outsole 2 are each divided into parts in a front-rear direction at the first and second divide portions D1, D2 (see FIG. 7).

As shown in FIG. 9, the second inclined surface 12F of the second portion 12 is configured so that it can rotate relative to the first inclined surface 11F of the first portion 11 in such a manner that the lower portion of the first divide portion D1 opens. As shown in FIG. 10, the fourth inclined surface 13B of the third portion 13 is configured so that it can rotate relative to the third inclined surface 12B of the second portion 12 in such a manner that the lower portion of the second divide portion D2 opens.

In FIG. 5, the position of the medial edge 1M of the upper end of the first divide portion D1 is set in the range of 65% to 75%, from the rear end 1B of the main sole MS, of the maximum length Lm from the front end 1F to the rear end 1B of the main sole MS, along the center axis S (FIG. 4) extending in the front-rear direction FB of the main sole MS.

The position of the lateral edge 1L of the upper end of the first divide portion D1 is set in the range of 60% to 70%, from the rear end 1B of the main sole MS, of the maximum length Lm of the main sole MS, along the center axis S of the main sole MS.

With the first divide portion D1 set in such a range, the line obtained by aligning the upper end of the first divide portion D1 with the width direction DW of the main sole MS is arranged posterior DB to the metatarsal phalangeal joints MP of the first toe B1 to the fifth toe B5 and is arranged anterior DF to the bases B11, B51 of the first to fifth metatarsal bones B1, B5. More preferably, the line is arranged posterior DB to the heads B12, B52 of the metatarsal bones. Note that the base refers to a portion of each bone that is close to a joint posterior thereto and that is slightly expanding to a greater thickness, and it is referred to also as the proximal head. On the other hand, the head refers to a portion of each bone that is close to a joint anterior thereto and that is slightly expanding to a greater thickness, and it is referred to also as the distal head.

In FIG. 4, the first divide portion D1 has a shape that is protruding toward the front direction DF as seen in a plan view. On the other hand, the second divide portion D2 has a shape that is protruding toward the rear direction DB as seen in a plan view.

In the present embodiment, the first portion 11 is continuous without being divided from the first divide portion D1 to the tip of the main sole MS. The first portion 11 defines a groove 11G, the groove 11G of FIG. 1 being shallower than the depth of the first divide portion D1 and extending in the width direction DW of the main sole MS of FIG. 4.

The second portion (rear portion) 12 extends toward the front direction DF from the rear surface. The second portion 12 defines a groove 12G anterior DF to the rear surface. The groove 12G is shallower than the depth of the second divide portion D2 (FIG. 1) and extends in the width direction W of the main sole MS.

Next, the paddle 5 of FIG. 8 will be described.

The paddle 5 is formed from a member different from the main sole MS. The elastic modulus of the paddle 5 is greater than or equal to the elastic modulus of the insole 4 and, more preferably, greater than the elastic modulus of the insole 4. The paddle 5 is formed from a resin-made flat plate having a thickness of 0.1 mm to 5.0 mm, more preferably 0.5 mm to 1.5 mm.

The paddle 5 is arranged so as to extend across the first to third portions 11 to 13. The paddle 5 is sandwiched between the upper surface of the midsole 1 and the lower surface of the insole 4. The paddle 5 includes a bridging portion 5F on the forefoot side, and a bridging portion 5B on the rear foot side.

A portion of the bridging portion 5F on the forefoot side of FIG. 8 is arranged between the insole 4 and the first portion 11. On the other hand, another portion of the bridging portion 5F is arranged between the insole 4 and the second portion 12.

A portion of the bridging portion 5B on the rear foot side is arranged between the insole 4 and the second portion 12. On the other hand, another portion of the bridging portion 5B is arranged between the insole 4 and the third portion 13.

In order for the bridging portion 5F on the forefoot side of FIG. 8 to be positioned with respect to the main sole MS, the first engagement portion 11E is formed on the upper surface of the first portion 11 and the second engagement portion 12E is formed on the upper surface of the second portion 12. The first portion 11 and the second portion 12 of FIG. 7 define the first depression and the second depression, respectively, into which the bridging portion 5F (FIG. 8) fits, wherein the first depression and the second depression form the first and second engagement portions 11E and 12E, respectively.

In order for the bridging portion 5B on the rear foot side of FIG. 8 to be positioned with respect to the main sole MS, the second engagement portion 12E is formed on the upper surface of the second portion 12 and the third engagement portion 18E is formed on the upper surface of the third portion 13. The second portion 12 and the third portion 13 of FIG. 7 each define a depression into which the bridging portion 5B (FIG. 8) fits, wherein the depressions form the respective engagement portions 11E, 12E.

In FIG. 5, the widths 5Wf, Wb of the bridging portions 5F, 5B of the first and second divide portions D1, D2 are each set to be 25% to 100% of the width W of the main sole MS.

In FIG. 8, the bridging portions 5F, 5B define a plurality of through holes 5H. The through holes 5H on the forefoot side are arranged so as to extend from the first portion 11 to the second portion 12. The through holes 5H on the rear foot side are arranged so as to extend from the second portion 12 to the third portion 13.

Note that it is preferred that the through holes 5H on the rear foot side are so structured that the third portion 13 can easily be displaced in the width direction DW.

The bridging portion 5F on the forefoot side of FIG. 8 is provided so as to bridge between the first portion 11 and the second portion 12 across the first divide portion D1, and the bridging portion 5F connects between the first portion 11 and the second portion 12 so that the inclined surface 12F of the second portion 12 is rotatable relative to the inclined surface 11F of the first portion 11, as shown in FIG. 9.

The bridging portion 5B on the rear foot side of FIG. 8 is provided so as to bridge between the second portion 12 and the third portion 13 across the second divide portion D2, and the bridging portion 5B connects between the second portion 12 and the third portion 13 so that the inclined surface 12B of the second portion 12 is rotatable relative to the inclined surface 13B of the third portion, as shown in FIG. 10.

In FIG. 4, the second divide portion D2 includes a diagonal portion 131 that extends toward the medial side in a diagonal forward direction DF from a central portion 13C between the medial side and the lateral side. The angle α formed between a virtual transverse (horizontal) line VL that is perpendicular to the center axis S extending in the front-rear direction FD of the main sole MS and the diagonal portion 131 of the second divide portion D2 is set in a range of 10° to 40°.

The medial edge 1M of the second divide portion D2 is arranged posterior DB to the lateral edge 1L of the second divide portion D2.

In the rear foot portion, a medial side surface 31 of the upper 3 of FIG. 1 includes a medial-side high rigidity portion 31H and a medial-side flexible portion 31S that is more flexible than the medial-side high rigidity portion 31H, which are separated from each other in the front-rear direction. A lateral side surface 32 of the upper 3 of FIG. 2 includes a lateral-side high rigidity portion 32H and a lateral-side flexible portion 32S that is more flexible than the lateral-side high rigidity portion 32H.

The front edge portion of the medial-side high rigidity portion 31H and/or the medial-side flexible portion 31S of FIG. 1 extend in an upper-rear diagonal direction from the upper end portion of the medial edge 1M of the second divide portion D2. The front edge portion of the lateral-side high rigidity portion 32H and/or the lateral-side flexible portion 32S of FIG. 2 extend in an upper-rear diagonal direction from the upper end portion of the lateral edge 1L of the second divide portion D2. Note that the term “from the upper end portion” means from the upper end or a vicinity thereof.

The high rigidity portions may each be formed from a synthetic-resin plate, for example. The low rigidity portions may each be formed from a fabric (cloth) such as a mesh fabric, a knit fabric, a woven fabric or a non-woven fabric, for example.

A plurality of strip-shaped restraining members 34M are arranged on the medial-side flexible portion 31S of FIG. 1 for restraining the stretch of the medial-side flexible portion 31S in the front-rear direction FB. Another plurality of strip-shaped restraining members 34L are arranged on the lateral-side flexible portion 32S of FIG. 2 for restraining the stretch of the lateral-side flexible portion 32S in the front-rear direction FD.

The restraining members may be a comb-shaped thin film bonded or welded (including transfer printing) on the surface of the mesh fabric.

In the forefoot portion, including directly above the first divide portion D1, the flexible portion 385 of the upper 3 is formed from a low rigidity material, e.g., a cloth-like fabric such as a mesh fabric, a knit fabric, a woven fabric or a non-woven fabric, for example. The flexible portion 35 as described above allows the inclined surface 12F of the second portion 12 to rotate while moving in an upper-front diagonal direction as shown in FIG. 9.

Next, a part of a shoe manufacturing process will be described.

As shown in FIG. 8, the paddle 5 is adapted to the engagement portions 11E to 13E, which are depressions in the first, second and third portions 11 to 13, thereby attaching (bonding) the paddle 5 to the upper surface of the midsole 1. Thus, the first portion 11 and the second portion 12 are positioned with respect to each other, and the second portion 12 and the third portion 13 are positioned with respect to each other.

The midsole 1, which is made integral by means of the paddle 5, is bonded to the reverse surface of the insole 4, which is integral with the upper 3 (not shown; FIG. 1). At this point, although the insole 4 and the upper 3 are surrounded by a last well known in the art, the midsole 1 is not divided in the front-rear direction as described above so that the midsole 1 can easily be positioned with respect to the insole 4 at the time of bonding.

Next, the behavior of the forefoot portion of the shoe while running will be described.

When not worn (FIG. 2), the first inclined surface 11F and the second inclined surface 12F of the first divide portion D1 are partly in contact with each other, and there may be a slight gap between the first inclined surface 11F and the second inclined surface 12F of the first divide portion D1 due to manufacturing errors. However, at the standstill position with the shoe on or at foot-flat while running, the first inclined surface 11F and the second inclined surface 12F contact each other with a strong pressure due to compressive deformation of the midsole 1, etc. Therefore, it will be possible to stably support the foot.

At heel-rise, the upper 8 and the main sole MS flex as shown in FIG. 9, and the second portion 12 is displaced so as to rotate relative to the first portion 11. As described above, the midsole 1 is attached to the upper 3 via the paddle 5 (FIG. 8). Therefore, the second portion 12 rotates, relative to the first portion 11, about the vicinity of the upper end of the first divide portion D1.

On the other hand, although the forefoot portion of the upper 3 is compressed, the flexible portion 385 of the upper 3 directly above, and anterior/posterior to, the first divide portion D1 of the present embodiment is formed from a flexible material such as a mesh fabric described above, for example, and the flexible portion 35 can easily be creased 35W, thereby making it unlikely that the rotation is inhibited. For example, the flexible portion 35 has no defined center of flexion, and therefore the inclined surface 12F of the second portion 12 rotates while moving in the upper-front diagonal direction in accordance with the flexion of the foot.

Next, the structure of the rear foot section of a human will be described briefly with reference to FIG. 11A to FIG. 12B.

As shown in FIG. 11A to FIG. 11C, the subtalar joint (STJ) and the midtarsal joint (MTJ) exist below the ankle. These joints STJ and MTJ can rotate about the axis Ss and the axis Sm, respectively. These axes Ss and Sm are orthogonal to intersecting planes Bs, Bm. The intersecting planes Bs, Bm are inclined planes that are inclined by about 42° and 15° with respect to the vertical plane in FIG. 11A and FIG. 11C. The intersecting planes Bs, Bm are also inclined planes that are inclined by about 20° and 9° with respect to the longitudinal axis of the foot in FIG. 11B.

Considering the angles of the intersecting planes, the angle α2 formed between the inclined surfaces 12B, 13B of the second divide portion D2 of FIG. 2 and the vertical plane is preferably about 5° to 45° on the lateral side of the foot, more preferably about 10° to 40°, and most preferably about 15° to 35°.

On the other hand, the angle α1 between the inclined surfaces 12F, 13F of the first divide portion D1 of FIG. 2 and the vertical plane is preferably about 20° to 70° on the lateral side of the foot, more preferably about 25° to 65°, and most preferably about 30° to 60°.

Next, the mechanism of the pronation occurring while running will be described briefly.

After landing while running, first, the joint STJ of FIG. 11A to FIG. 11C rotates, and the heel thereby pronates as shown in FIG. 12A. Then, the joint MTJ rotates in conjunction with the rotation of the joint STJ of FIG. 11A to FIG. 11C, and the lower leg thereby medially rotates as shown in FIG. 12B. Thus, pronation occurs. In order to realize movements of joints that are close to barefoot running, it is believed that there is a need for a shoe structure that allows, without inhibiting, the action of the joints STJ, MTJ, the pronation and the internal rotation.

Next, the behavior of the rear foot portion of the foot while running will be described.

In the main sole MS of the embodiment of FIG. 1, the second divide portion D2 of the rear foot section extends in an upper-rear diagonal direction, the second divide portion D2 of FIG. 5 includes the diagonal portion 131 on the lateral side. Therefore, immediately after landing such as first strike of FIG. 10, the lower portion of the second divide portion D2 is displaced so as to open, and it is unlikely to inhibit the action of the joints STJ, MTJ of FIG. 11A to FIG. 11C, the pronation of FIG. 12A and the internal rotation of FIG. 12B. Therefore, it is likely to realize an action of pronation that is proximate to that during barefoot running.

On the other hand, immediately after landing, a large impact load is applied to the third portion 13 of FIG. 10. However, at the second divide portion D2, the third portion 13 and the second portion 12 are in contact with each other and are separated from each other. Therefore, the third portion 13, which is separated from the second portion 12, will easily deform after landing. Therefore, a good shock-absorbing property will be realized.

During the transition from heel-contact of FIG. 10 to foot-flat of FIG. 2, the second portion 12 is in contact with the third portion 13. Therefore, the transition will go smoothly. Thus, it is likely that movements of joints during barefoot running will be realized.

Immediately after landing as shown in FIG. 10, the main sole MS flexes, and the third portion 13 is displaced so as to rotate relative to the second portion 12. As described above, the midsole 1 is attached to the upper 3 via the paddle 5 (FIG. 8). Therefore, the third portion 13 rotates, relative to the second portion 12, about the vicinity of the upper end of the second divide portion D2.

On the other hand, as can be seen from a comparison between FIG. 2 and FIG. 10, at heel-contact immediately after landing, an area of the upper 3 that is in an upper-rear diagonal direction of the second divide portion D2 is compressed as the third portion 13 rotates relative to the second portion 12. Since the upper 3 of the present embodiment includes the flexible portions 328, 31S (FIG. 1), the flexible portions 328, 31S (FIG. 1) of FIG. 2 will easily contract (creating creases) as shown in FIG. 10. Thus, the rotation at the second divide portion D2 is unlikely to be inhibited.

At heel-rise of FIG. 9, the heel of the foot is likely to rise inside the upper 3. In the present embodiment, while the flexible portions 328, 31S (FIG. 1) are present, the restraining members 34L, 34M (FIG. 1) are provided on the flexible portions 328, 31S (FIG. 1). Therefore, it is possible to restrain the stretch of the flexible portion of the upper 3 at heel-rise, and it is as a result possible to prevent the heel from rising inside the upper 3.

Next, a reference example and test examples will be illustrated in order to elucidate the advantageous effects of the present embodiment.

First, as a reference example, test sample T1 of FIG. 13A was provided that did not have the divide portions D1, D2. On the other hand, test samples T2 to T5 of FIG. 13B to FIG. 13E were provided as test examples.

In sample T2, the main sole MS is divided along a plane that is orthogonal to the axis Ss (FIG. 11A). In sample T3, the main sole MS is divided at four divide portions D1, D2, D11, D21 along planes that are orthogonal to the axis Ss (FIG. 11A) and the axis Sm (FIG. 11A). In samples T4 and T5, diagonal flexible portions 33S are provided on the medial side and the lateral side of the upper 3 so as to function in conjunction with the divide portions D1, D2 of samples T2 and T3. Note that sample T1 is not provided with the divide portions and the flexible portions.

A test experiment was conducted with one subject at a running speed of 4 min/km. Comparisons were made between running with shoes of FIG. 13A to FIG. 13E and running barefoot. The flexion/extension angle of the foot joint was measured while running, and the ground reaction force was measured in the front-rear direction and in the vertical direction.

Then, the maximum propulsion force and the propulsion impulse (impulse product) were calculated from the angle and the ground reaction force in the front-rear direction. The values are shown in FIG. 14A and FIG. 14B. These graphs indicated that samples T2, T3, T4, T5 having the divide portions, as compared with barefoot and sample T1, required a greater maximum propulsion force and a greater propulsion impulse while running at the same speed.

FIG. 14C shows a comparison result for the work of the foot joint required for push-off. As can be seen from the figure, the amount of work is greater for samples T2, T3, T4, T5 provided with the divide portions than for barefoot and sample T1. It can be seen that this resulted in a greater load on the lower leg.

The reason for such results is assumed to be because the triceps of the lower leg, which are important for running, are used more due to the significant decrease in the rigidity of the main sole MS. Therefore, by running with these shoes on, one can expect a high effectiveness in training.

Then, the heel portion pronation angle β and the lower leg internal rotation angle γ of FIG. 12A and FIG. 12B were calculated from the flexion/extension angle. The results are shown in FIG. 15A and FIG. 15B. As a result of comparing the heel portion pronation angle β, it can be seen that sample T1 has a greater absolute value of the pronation angle β than barefoot, whereas samples T2, T3, T4, T5 have joint angles closer to barefoot running. As for the lower leg internal rotation angle γ, sample T1 has a smaller absolute value of the internal rotation angle γ than barefoot, whereas samples T2, T3, T4, T5 have joint angles closer to barefoot running.

Therefore, it can be seen that with the provision of the second divide portion D2 of FIG. 10, more preferably with the provision of the groove 12G and the flexible portions 32S, 31S (FIG. 1), it is possible to realize a shoe with which joint movements are closer to barefoot running.

Then, the value of the impact load was calculated by dividing the ground reaction force in the vertical direction by the unit time. The results are shown in FIG. 15C. It can be seen from the figure that samples T2, T3, T4, T5 have an equivalent shock-absorbing property to sample T1, and have a good shock-absorbing property with a smaller impact value than barefoot.

Samples T2 to T5 of FIG. 13B to FIG. 13E were produced by modifying the main sole MS and the upper 3 of existing shoes. Therefore, they do not have the paddle (FIG. 8).

A shoe of the present invention may have a structure like those of samples T2 to T5, or may have a structure of samples T2 to T5 with the paddle (FIG. 8) added thereto.

The bridging portions 5F, 5B of the paddle 5 of FIG. 8 may be separated from each other. However, the paddle 5 being continuous from the first portion 11 to the third portion 13 has a greater Young's modulus than the midsole 1, and will be useful as a reinforcement device of the second portion 12.

When the paddle 5 of FIG. 8 is provided, the through holes 5H do not need to be provided in the paddle 5. When the through holes 5H are provided, protruding portions may be formed on the upper surface of the midsole 1 so as to correspond to the through holes 5H, so that the upper surface of the midsole 1 in the through holes 5H is set to be at about the same level (height) as the upper surface of the paddle 5.

As in the alternative example of FIG. 16, this shoe may be provided with grooves Gm arranged in a staggered pattern on the lower surface of the main sole MS and on the upper surface of the main sole MS.

FIG. 17A to FIG. 17D show alternative examples.

As shown in the examples of these figures, at the divide portions D1, D2, the sections 11, 12, 18 of the main sole may be in contact with each other via bridging portions 5F, 5B that are protruding downward. At the divide portions D1, D2, the bridging portions 5F, 5B may be such that the midsoles are not in direct contact with each other, but outsoles are in direct or indirect contact with each other.

FIG. 17E to FIG. 17G show other alternative examples.

In these figures, the upper surface of the midsole 1 is attached to the lower surface of the insole 4, and the paddle 5 (FIG. 8) is absent. In these cases, the midsoles 1 may be bound together in areas other than the divide portions D1, D2 via a bonded or welded attachment portion 19 that is dotted in the figure. That is, the midsole 1 may form the bridging portions 5F, 5B.

While preferred embodiments have been described above with reference to the drawings, various obvious changes and modifications will readily occur to those skilled in the art upon reading the present specification.

For example, the midsole may be provided with gel or pod-like shock-absorbing parts. The main sole may be formed solely from a flexible midsole-like material or solely from an outsole.

Thus, such changes and modifications are deemed to fall within the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention is applicable to various shoes for running, walking, training, etc.

REFERENCE SIGNS LIST

-   -   1L: Lateral edge, 1M: Medial edge     -   12: Rear portion (second portion), 12B: Inclined surface, 12E:         Engagement portion     -   13: Rear end portion (third portion), 13B: Inclined surface,     -   13C: Central portion     -   13E: Engagement portion, 131: Diagonal portion     -   3: Upper, 31H: Medial-side high rigidity portion, 31S:         Medial-side flexible portion, 32: Lateral side surface     -   34L: Restraining member, 34M: Restraining member     -   4: Insole, MS: Main sole     -   5H: Through hole     -   D2: Divide portion, DB: Posterior, DF: Anterior, FB: Front-rear         direction, S: Center axis     -   VL: Transverse line     -   α: Angle 

1. A shoe comprising: an upper configured to wrap around an instep of a foot; and a main sole configured to support a sole of the foot, wherein: the main sole includes a rear end portion on a rear end side, and a rear portion arranged anterior to the rear end portion; a rear surface of the rear portion includes one inclined surface extending in an upper-rear diagonal direction; a front surface of the rear end portion includes another inclined surface extending in the upper-rear diagonal direction; the one inclined surface of the rear portion and the other inclined surface of the rear end portion together define a divide portion at which the one and other surfaces are in contact with each other or are capable of contacting each other; and the other inclined surface of the rear end portion is set so that the other inclined surface is rotatable relative to the one inclined surface of the rear portion in such a manner that a lower portion of the divide portion opens.
 2. The shoe according to claim 1, wherein the divide portion includes a diagonal portion extending, from a central portion in a medial-lateral direction, in an anterior lateral diagonal direction.
 3. The shoe according to claim 2, wherein an angle formed between (i) a virtual transverse line perpendicular to a central axis, which extends in a front-rear direction of the main sole, and (ii) the diagonal portion of the divide portion is set in a range of 10° to 40°.
 4. The shoe according to claim 1, wherein a medial edge of the divide portion is arranged rearward of a lateral edge of the divide portion.
 5. The shoe according to claim 1, further comprising: an insole being continuous with the upper and configured to cover the sole of the foot, the main sole covering the insole from below; and a bridging portion provided on the rear portion and the rear end portion so as to bridge the divide portion, wherein the bridging portion connects between the rear portion and the rear end portion so that the one inclined surface of the rear portion is rotatable relative to the other inclined surface of the rear end portion, wherein: a part of the bridging portion is arranged between the insole and the rear portion; and another part of the bridging portion is arranged between the insole and the rear end portion.
 6. The shoe according to claim 5, wherein the bridging portion is formed from a plate-shaped member that is different from the main sole.
 7. The shoe according to claim 6, further comprising one engagement portion and another engagement portion for positioning the bridging portion, wherein the one engagement portion is formed on an upper surface of the rear portion, and the other engagement portion is formed on an upper surface of the rear end portion.
 8. The shoe according to claim 7, wherein the rear portion and the rear end portion define respective depressions into which the bridging portion fits, the depression of the rear portion forms the one engagement portion and the depression of the rear end portion forms the other engagement portion.
 9. The shoe according to claim 6, wherein an elastic modulus of the bridging portion is equal to or greater than an elastic modulus of the insole.
 10. The shoe according to claim 6, wherein the bridging portion defines a through hole, the through hole being arranged so as to extend from the rear portion to the rear end portion.
 11. The shoe according to claim 6, wherein a width of the bridging portion in the divide portion is set to be 25% to 100% of a width of the main sole.
 12. The shoe according to claim 6, wherein a thickness of the bridging portion is set to be 0.1 mm to 5.0 mm.
 13. The shoe according to claim 1, wherein the rear portion extends toward a front direction from the rear surface, the rear portion defines a groove anterior to the rear surface, and the groove is shallower than a depth of the divide portion and extends in a width direction of the main sole.
 14. The shoe according to claim 1, wherein: a medial surface of the upper includes a medial high-rigidity portion and a medial flexible portion that bends more easily than the medial high-rigidity portion, wherein the medial high-rigidity portion and the medial flexible portion are separated from each other in a front-rear direction; a lateral surface of the upper includes a lateral high-rigidity portion and a lateral flexible portion that bends more easily than the lateral high-rigidity portion, wherein the lateral high-rigidity portion and the lateral flexible portion 32S are separated from each other in the front-rear direction; at least one of (i) a front edge portion of the medial high-rigidity portion and (ii) the medial flexible portion extend in an upper-rear diagonal direction from an upper end portion of a medial edge of the divide portion; and at least one of (i) a front edge portion of the lateral high-rigidity portion and (ii) the lateral flexible portion extend in the upper-rear diagonal direction from an upper end portion of a lateral edge of the divide portion.
 15. The shoe according to claim 14, wherein: a strip-shaped restraining member is arranged on the medial-side flexible portion for restraining stretch of the medial-side flexible portion in the front-rear direction; and another strip-shaped restraining member is arranged on the lateral-side flexible portion for restraining stretch of the lateral-side flexible portion in a front-rear direction. 